Some of us have a vague memory of John C. Fremont - the man who charted the course from St. Louis to California. He was more than that, says his biographer Tom Chaffin. He was so successful at mapping and scientific observation that he soon found himself in a number of military and political roles, for which he was not well suited. They included command in the Mexican-American War and the Civil War as well as governor of California and Republican candidate for president in 1856. Nonetheless, his geography and mapping was so good, he paved the way for the expansion of the United States to the Pacific.

GUESTS

Tom Chaffin, University of Tennessee, Knoxville and author of "Pathfinder: John Charles Fremont and the Course of American Empire"